Known road finishers comprise a material hopper for receiving paving material that is at the front of the road finisher's towing vehicle with respect to a paving travel direction. During paving, the paving material is conveyed from the material hopper to a rear portion of the road finisher via a suitable longitudinal conveying device. There, the paving material is distributed transversely to the paving travel direction using a distribution auger and is thus fed uniformly to a paving screed pulled behind by the towing vehicle for compacting the paving material. It is known that working components of the paving screed, such as tamper bars, smoothing plates and/or press bars, are heated electrically or with gas to prevent the hot paving material from sticking to the working components. In the case of electric heating, resistance heating elements are distributed in the paving screed, which are supplied with three-phase current by a three-phase generator provided on the towing vehicle.
EP 1 036 883 B1 found that permanent operation of the electric heating elements of the paving screed at full power places a heavy load on the three-phase generator under unfavorable operating conditions and can also have low energy efficiency. In order to solve these problems, it is proposed that the electric heating elements of the paving screed should be switched in cycles. From a three-phase generator provided on the towing vehicle, supply lines lead to the electric heating elements integrated on the two screed halves (left and right screed half) of the paving screed. Contactors are provided in the supply lines outside the paving screed. The temperature of the three-phase generator is monitored by using temperature-dependent resistors in the windings of the three-phase generator. If the temperature of the generator exceeds a certain threshold value, the operation of the heating elements of the paving screed is switched to clocked operation. This means, for example, that the heating elements of the left screed half are switched off for a predetermined period of time, e.g., 30 seconds, and only the heating elements in the right screed half remain switched on. When the predetermined time has elapsed, the heating elements of the right screed half are switched off and the heating elements of the left screed half are switched on again. This is repeated permanently, allowing the three-phase generator to cool down again. Although such a system can protect the generator against overheating, the achievable energy efficiency can still be improved.
EP 1 295 990 B2 discloses a road finisher with a paving screed with a base screed part and extension parts provided on both sides thereof to increase the paving width. The paving screed is divided into four sections, of which two are positioned on the base screed and one on each of the two extension parts. Four resistance heating elements are provided in each of the sections to heat the respective screed section. The heating elements are connected to a generator of the road finisher via relay switches provided outside the paving screed for energy supply, with a common relay switch connected upstream of two adjacent heating elements. With a control device, the relay switches corresponding to the heating elements of a section are closed to feed the heating elements if a temperature measured at the section is below a first threshold value. If the measured temperature exceeds a higher, second threshold value, the associated relay switches are opened again to interrupt the heating of the section. This is to keep the screed sections in a suitable temperature window. A particular disadvantage of this system is the high cabling effort. In addition, the energy efficiency can still be improved here.